Mounting for work centers and the like



Oct. 16, 1951 w. G. HOELSCHER 2,571,363

MOUNTING FOR WORK CENTERs AND THE LIKE Filed June 3, 1948 Z 204229149 i //////I MW M if' ,fz T54 INVENTOR.

Patented ct. 16, 195i UNITED STATES PATENT OFFICE MOUNTING FOR WOIECENTERS AND THE Application June 3, 1948, Serial No. 30,905

1 claim. 1

This invention relates to an improved mounting for lathe centers and the like. These lathe center mountings are incorporated in the conventional tailstock as currently employed in lathe construction. More specically, the invention relates to a mounting which will permit the work centering element to move relative to the tailstock when undue axial pressure is put upon the center as occurs when the work expands in the course oi the cutting operation.

In the development of this art there have been a number of devices disclosed and claimed in patents which have had the purpose of permitting expansion of the work. One of the earlier examples of this type of device is found in the patent to Muller, No. 1,318,223, issued October 7, 1919, wherein a spring was employed to permit yielding of the work center in accordance with the expansion of the work. However, as the art of turning has developed, that is, with the advent of high speed tools and the procedureof dry cutting, the amount of heat generated in the work has increased. It will be seen that the tailstock structure and the work center mounting must be of rugged construction to properly support the work under these conditions7 and yet at the same time, the device, permitting axial expansion of the work, must do so readily and in the proper amount.

Accordingly, it has been the object of the present inventor to provide an improved work center mounting relative to a tailstock which incorporates an arrangement of elements permitting the work center to move relative to the tailstock as the work expands, the improved mounting providing for a stabilized support for the work center under normal conditions and throughout any phase of expansion within the proper limits, but sensitive enough to accommodate the expansive force easily without interfering with the proper support of the work. In other Words, it is vital that the worls` be rmly held between the work centers, that is the headstock and tailstock, under the extremely heavy lateral pressures imposed by the high speed cutting tool, and the ability of the work center to yield under expansive pressure or force should in no way detract from the stability and eciency of the work support.

It has been a still further object of the present inventor to provide a mounting device for the above purpose which is exceedingly simple and which may readily be incorporated in the normal mounting of the work center without radical change in design. In other words, a minimum of parts are interposed and the ele- 2 ments utilized are of the utmost simplicity and are so related as to be easily assembled.

Other objects and certain advantages relative to the specific structure of the mounting will be more fully apparent from the description of the drawings in which:

Figure 1 is a diagrammatic general View looking at the side of the lathe and illustrating a piece of work in position between work centers, the conventional tailstock structure for the one Work center being generally illustrated.

Figure 2 is an enlarged side view of the tailstock, the upper part thereof being broken away diametrically through the axis of the work center for illustrating the details of the mounting.

Figure 3 is an enlarged sectional View taken on line 3 3, Figure 2, further illustrating the tailstock and showing the principal element of the Work center mounting which permits the work center to move under expansive force.

Figure 4 is a sectional view taken on line 4 4, Figure 3, showing in enlarged detail, the improved mounting for the work center.

Referring to the drawings, particulary Figure 1, the tailstock is generally indicated at I0, the work at I I, the work center, mounted in the tailstock, at I2 and the headstock work center at I3. Inasmuch as the mounting of the tailstock on the lathe bed is not part of this invention, the details pertaining to this are not illustrated.

For the purpose of the present invention, it is Sufficient to state that the tailstock includes primarily a main body element generally illustrated at I4. A bore I5 is providedrhorizontally or lengthwise of the tailstock body in the upper portion thereof. A sleeve or spindle I6 is mounted for movement axially within the bore I5, the upper part of the tailstock body constituting a quill or housing for this sleeve. Rotative motion of the sleeve is prevented by means of a key Il disposed in a groove I8 along the underside of the sleeve. The work center element I9 is supported in a bore 20 in the forward end of the sleeve I5 by means of ball bearings and other elements hereinafter described. The work center includes the usual pointed end 2I and the shank 22.

Movement of the sleeve for adjusting the work center relative to the work after the tailstock has been set in position on the lathe bed is accomplished by means of a screw 23 screw-threaded through a nut 24 fixed in a bore 25 at the rear end of the sleeve in axial alignment with the work center, that is, on the axis of the sleeve. A bore 26 connects the bore 2U and the bore 25, this connecting bore 26 being of sulicient size to provide clearance for the inwardly extended end of the screw 23. The screw includes a rearwardly extended portion 21 which is plain and which is rotatively mounted in a support cap 28 secured against the rear end of the quill. This cap includes a screw-threaded portion screw` threaded into the rear end of the bore I of the quill. The screw rod includes a shoulder 30 lying against a Washer 3l and the washer engaged against an end thrust bearing 32 mounted in the inner wall of the cap.

A hand wheel 33 is engaged on a counterturned portion 34 of the screw rod 23. A key 35 holds the hand Wheel in xed rotative connection with the screw rod. A nut 35 screwthreaded on the end of the portion 34 holds the hand wheel against the rear end of the cap and draws the shoulder 3E) against the inner end of the cap through the Washer and bearing. Thus, the screw rod may be rotated in the cap and its threads caused to traverse the nut 24 whereby the sleeve I6 is translated for adjusting the work center.

The work center element is supported in an assembly of anti-friction bearings. As stated, it includes the usual pointed end portion and shank. Further, between these portions, it includes a shoulder 4U, the inner end of which constitutes an abutment engaging the inner race of an adjacent anti-friction bearing 4 I. A multiplicity of bearings is used, there being six in this case, four in the forward set and two in the rearward set. The sets are spaced apart by means of inner and outer spacer elements 42 and 43. The inner races of the respective bearings and the inner Spacer element are held against the shoulder 40 by means of a nut 44 screwed on the inner counterturned screwthreaded portion of the shank. This nut is locked in position by means of a set screw 45 engaging a clamping shoe 46. A cap 41 is secured to the outer or forward end of the sleeve I6 by means of screws 48. This cap overhangs the outer race of the outermost bearing and prevents outward displacement of the bearings.

The bore which houses the Work center and the ball bearings extends inwardly beyond the nut 44, and the shoulder 49 constituted by the bottom of this bore provides the supporting surface for the elements of the device which permits movement of the work center relative to the sleeve when b the work expands. Three elements constitute the preferred device, one of these being a circular abutment plate 50 which lies against the shoulder 49. This element consists of a plain disc with the exception of its forward face. The forward face includes a counterturned portion or outer circular groove 5I. This groove is of a radial width approximately a little less than one-half of the radius of the disc.

The second element of the device consists of a sleeve or annulus 52 fitting snugly within the bore and engaging the outer race 53 of the rearmost bearing 4I. This sleeve or annulus encircles the nut 44 and is clear thereof. The third member of the device consists of a plain disc 54 having slightly rounded edges. This disc, like the abutment disc, ts snugly within the bore which houses the work center. Disc 54 is made from a grade of flexible steel suitable to permit the disc to yield for a limited distance under abnormal pressure but having sufcient stiffness to maintain a normal pressure against the work center without yielding. As an example, s. A. E. 4145 steel, properly hardened, is found suitable for this purpose. The sleeve or annulus engages the outer margin of the intermediate disc 54 adjacent the clearance or relief groove of the abutment disc. In order to permit complete freedom or flexing of the disc 54, the corner of the bore in which the abutment disc rests, is grooved or relieved so that the rear corner of the abutment disc is clear of contact.

The bearing assemblies, the spacer sleeves and the three elements of the device are held snugly within the bore by means of the forward cap element 48. Accordingly, under normal conditions, that is, in the absence of undue pressure on the work center, the plain or intermediate disc 54 is not flexed nor distorted in any Way. However. in the event that pressure is exerted on the work center by expansion of the work, the thrust is carried back through the work center, through the ball bearings and to the outer margin of the intermediate disc 54 through the spacer sleeve or annulus 52 and reasonable amounts of expansive pressure will be taken up by flexing of the disc within the clearance afforded by the relief groove 5I in the abutment disc 5U. This thrust passes through the races of the bearings from the inner to the outer end through the annulus 52. The disc is stiff enough to prevent undue displacement of the work center under normal cutting pressures, but under the heavy pressure imparted by the expansive force or thrust, the disc will yield and permit the work expansion.

Having described my invention, I claim:

A resilient support structure for the rotatable work center of a tailstock adapted to rotatably support a longitudinal work piece under normal axial thrust and to yield axially to accommodate thermal expansion of the work piece, said rotatable work center having a shoulder near its forward end and having a shank extending rearwardly therefrom, said resilient support structure comprising, an internally cylindrical sleeve carried by the tailstock having its axis aligned with the axis of rotation of the work piece and having an end wall, a ball bearing assembly mounted within said sleeve, the ball bearing assembly having outer and inner races, said inner races being adapted to receive the shank of the work center and to engage the shoulder thereof, whereby the inner races collectively are adapted to support the work center rotatably and to transmit the axial thrust of the work center to the outer races, the outer races being slidably confined within the internally cylindrical sleeve to allow axial displacement of the ball bearing assembly by the Work center relative to said sleeve, a spacer sleeve slidably mounted within the internally cylindrical sleeve behind the rearward outer race of the I`ball bearing assembly, the spacer sleeve having its forward end engaged against the rearward outer race and providing a thrust element for the ball bearing assembly, the spacer sleeve having an inside diameter adapted to provide an annular clearance area for the shank and having a length dimension adapted to provide axial clearance for the rearward end of the shank, a circular abutment plate seated against the end wall of the internally cylindrical sleeve and being spaced axially from the rearward end of the spacer sleeve, 'the abutment plate having a forwardly extending central face and a depressed` annular margin of substantial width, and a flat abutment plate, the resilient disk being larger inY diameter than said central face to provide a mar--y gin overhanging said depressed annular margin, REFERENCES CITED the Spacer Sleeve having a Wan thickness sub' The followincir references are of record in the stantially less than the Width of the depressed me of this patcnt:

annular margin and being concentric with said central face, whereby the axial thrust of the Work 5 UNITED STATES PATENTS center is imposed by the spacer sleeve upon the Number Name Date overhanging margin of the resilient disk, said 1,966,409 Hoelscher July 10,1934 overhanging margin of the resilient disk being 1,993,809 Schenelle Mar. 12, 1935 adapted to support the work center rmly against 2,124,164 Fritzsch July 19, 1938 normal axial thrust and to flex to accommodate 10 2,314,622 Klamp Mar. 23, 1943 thermal expansion of the work piece.

WILLIAM G. HOELSCHER. 

